The present invention relates in general to telecommunication techniques. More particularly, the invention provides a method and system including a squelch table update technique for optical networks. Merely by way of example, the invention is described as it applies to Bi-directional Line-Switched Ring (BLSR) in Synchronous Optical Network (SONET), but it should be recognized that the invention has a broader range of applicability.
Telecommunication techniques have progressed through the years. As merely an example, Synchronous Optical Network (SONET) has been used for conventional optical telecommunications for telephone applications. SONET defines a technique for transmitting multiple signals of different capacities through a synchronous, flexible, optical hierarchy. The SONET can terminate signals, multiplex signals from a lower speed to a higher speed, switch signals, and transport signals in the network according to certain definitions. Multiple SONET nodes may be interconnected into a ring structure to achieve high survivability. For example, if the SONET suffers from a connection failure at one location, the SONET can intelligently send the affected signals through one or more alternative routes without encountering the failure location. Such rerouting process is often known as automatic protection switching (APS). A Bi-directional Line-Switched Ring (BLSR) is a ring, which uses the SONET line-level status and performance parameters to initiate the APS process.
In a BLSR, a terminal is often called a node. The terminal is assigned to a node ID. The node ID identifies the SONET terminal within the BLSR. The Node IDS on a BLSR may not have consecutive values; hence the value of a Node ID usually does not imply any connectivity information but is merely the identification for a node in the ring. To represent the physical connectivity, a ring map contains a complete order of Node IDS. The ring map is usually available at each node along with a squelch table.
A squelch table includes a topological map of traffic at a specified node. For each STS channel that is terminated or passed through the specified node, the squelch table usually contains the source node ID of the incoming Synchronous Transport Signal (STS) channel and the destination node ID of the outgoing STS channel. The squelch table can be used to prevent traffic misconception in case of node failure or ring segmentation of BLSR. The squelching may be performed at the STS level or at the Virtual Tributary (VT) level.
From time to time, the squelch table at each node needs to be updated either manually or automatically. For example, when a node is removed from the ring or added to the ring, the squelch table should be updated. Some conventional protocols have been implemented to automatically update the squelch table. These conventional protocols, however, usually involve complicated mechanisms. It may take a long time to update the squelch table. Additionally, a large amount of traffic may be generated by these protocols which can lead to limited bandwidth being available for other management functions. Other limitations also exist with conventional BLSR techniques.
Hence it is highly desirable to improve squelch table update techniques for optical networks.